Investments - Amortized cost, gross unrealized gains and losses and fair value for fixed income securities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Schedule of Available for Sale Securities
Amortized cost, net	$ 61,451	$ 56,293
Gross unrealized gains	4,976	2,847
Gross unrealized losses	(73)	(96)
Fixed income securities	66,354	59,044
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost, net	3,129	4,971
Gross unrealized gains	94	141
Gross unrealized losses	(1)	(26)
Fixed income securities	3,222	5,086
Municipal
Schedule of Available for Sale Securities
Amortized cost, net	8,752	8,080
Gross unrealized gains	837	551
Gross unrealized losses	(2)	(11)
Fixed income securities	9,587	8,620
Corporate
Schedule of Available for Sale Securities
Amortized cost, net	47,226	41,090
Gross unrealized gains	3,981	2,035
Gross unrealized losses	(65)	(47)
Fixed income securities	51,142	43,078
Foreign government
Schedule of Available for Sale Securities
Amortized cost, net	1,013	968
Gross unrealized gains	42	16
Gross unrealized losses	0	(5)
Fixed income securities	1,055	979
ABS
Schedule of Available for Sale Securities
Amortized cost, net	1,260	860
Gross unrealized gains	15	8
Gross unrealized losses	(5)	(6)
Fixed income securities	1,270	862
MBS
Schedule of Available for Sale Securities
Amortized cost, net	71	324
Gross unrealized gains	7	96
Gross unrealized losses	0	(1)
Fixed income securities	$ 78	$ 419

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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